During the 4/1/81-3/31-82 grant year, a Nicolet 7199 Fourier transform infrared spectrometer, adapted for photoacoustic (PA) measurements at visible wavelengths, will be used to obtain visible PA spectra of whole blood and other condensed phases at a spectral resolution approaching 0.02 nm at 500 nm that exceeds the best resolution obtained by pulsed tunable dye laser-piezoelectric detector PA techniques. Microphonic and piezoelectric detection will be compared with particular concern given to the feasibility of reducing duration of spectral measurements in the visible to times of the order of two minutes required by present minicomputerized clinical transmittance spectrometers used to determine percent oxyhemoglobin, carboxyhemoglobin, and methemoglobin in blood samples. Numerical modeling of photoacoustic measurements in opaque liquid samples will be carried out on a DEK System 20 midicomputer. Theoretical results will be compared with pulsed laser PA experiments performed on whole blood and other opaque liquids. The feasibility of using PA detection techniques in electron paramagnetic resonance and nuclear magnetic resonance experiments on condensed phase samples will also be explored.